The negative impacts of economic stress on infants' development persist across the lifespan (Melrose et al., 2014). As such, understanding how early deficits pertaining to socioeconomic status (SES) emerge, and what processes potentially underlie the development of such deficits is a critical step toward the creation of efficient and effective intervention programs. It has been proposed that negative outcomes related to lower-SES or poverty are mediated by deficits in effortful control, and a model has been proposed suggesting that the link between SES and effortful control is mediated by allostatic load through processes such as a dysregulation of the hypothalamic-pituitary-adrenal axis resulting in maladaptive elevations in cortisol levels (Lengua, 2012). While the importance of effortful control is not contested, and the link between low-SES and decreased effortful control is well established, the mediating effect of cortisol on the link between low-SES and any cognitive outcomes is severely lacking in direct empirical support (Piccolo et al., 2014), and the full model has never been tested as it relates to effortful control specifically. Additionally, to my knowledge, no study has examined this model or even components of this model within the first six months of life. This is surprising given that cognitive outcomes pertaining to attentional control, an early developing component of effortful control, are significantly associated with SES by 6 months of age (Clearfield & Jedd, 2013). Thus, the current investigation seeks to advance the field's understanding of the emergence of SES related cognitive deficits by following infants at 3.5, 5, and 6.5 months of age and examining their attentional control capabilities in the context of their SES and basal cortisol levels. Furthermore, to establish a more complete picture of the developmental context of these infants, data about the stability of the home environment will be collected. Previous research has demonstrated significant mediating effects of factors of the home on the association between SES and infant cognitive abilities (Rubio-Codina, Attanasio, Grantham-McGregor, 2016). Accordingly, factors of the home environment, specifically chaos and adherence to routines, will be examined as potential mediators of the link between SES and basal cortisol levels. Given the fact that decreased effortful control is associated with poorer coping strategies in the context of economic stress in adolescence (Taylor, Widaman, & Robins, 2017), this project has the potential to greatly increase the mental health outcomes of economically disadvantaged youth by determining when and how such deficits emerge. This project would also be a great training opportunity as it would foster the development of an interdisciplinary research program incorporating physiological, behavioral, and environmental measures. This will be accomplished through supplementing my research skills and interdisciplinary background with 1) in-depth instruction and hands on experience with the collection and analysis of physiological data, 2) extensive training in longitudinal data collection and advanced statistical methods, 3) continued mentorship and explicit multi-faceted instruction in research ethics.